CATALYSIS OF HYDROSILYLATION XI. RHODIUM(I)-SILOXYALKYLPHOSPHINE COMPLEXES; SYNTHESIS, CHARACTERISTICS AND CATALYTIC ACTIVITY

Article abstract of DOI:10.1016/S0022-328X(00)99347-1

Rhodium(I) complexes with 1,5-cycloocatdiene (COD) and disiloxydiphosphines 2 where n = 1-3; (B-1, B-2, B-3, respectively)> and/or with trisiloxytriphosphine Ph2P(CH2)3(CH3)Si2 (C-2) were synthesized.Their composition and structure were determined using elemental analysis, molecular weight measurements and spectroscopic (IR, 1H NMR and vis) methods, and were then compared with the corresponding data for RuCl(COD)PPh3 (A) and RhCl(COD)2 (D).The analyitical and physico-chemical data all confirm the square planar geometry of the rhodium siloxyphosphine (the same as for rhodium triphenylphosphine) complexes with the general formula <(COD)RhCl(PPh2)(CH2)n>mZ where m =2 and Z =(CH3)2SiOSi(CH3)2 or m = 3 and Z = (CH3)2SiOSi(CH3)OSi(CH3)2. The structure is independent of the type of phosphine ligand, and the molar ratio of Rh : P is always 1 : 1. Catalytic activity of the complexes prepared was tested in the hydrosilylation of 1-hexene by triethoxysilane which showed a slight decrease in turnover number (A-C) compared with Wilkinson's catalyst (E) but the activation energies for the rhodium-siloxyphosphine complexes (B and C) are higher than those for the rhodium phosphine complexes (A and E).